[DOC]: Convert to single sphinx project so full ToC is visible from subprojects

[alliepiper]

Is this a duplicate?

• I confirmed there appear to be no duplicate issues for this bug and that I agree to the Code of Conduct

Is this for new documentation, or an update to existing docs?

Update

Describe the incorrect/future/missing documentation

The ToC with all top-level projects disappears once you click on a subproject. This is undesirable. Find a way for the top-level ToC to persist.

If this is a correction, please provide a link to the incorrect documentation. If this is a new documentation request, please link to where you have looked.

No response